The present invention concerns a transmission unit for motor vehicles, and in particular to the type whereby the transmission ratio is regulated steplessly by means of a continuously variable transmission.
It is known that such transmission units, apart from the actual transmission, are provided with a hydraulic cylinder/piston unit to set the transmission ratio of the continuously variable transmission. It is also known that such transmission units can be equipped with a pressure compensation chamber to compensate increases of pressure in the piston chamber of the cylinder/piston unit resulting from centrifugal forces, whereby this pressure compensation chamber is connected with said piston chamber via a filler port.
It is also known that this filler port can be provided with a passage organ having a passage opening with very precise dimensions, for example as described in Dutch patent application No 8302089.
The known passage organs are disadvantageous in that they are composed of different parts, which considerably increases the risk of manufacturing faults as well as the total cost of production.
Another disadvantage consists in that the passage openings in these existing passage organs are mainly situated centrally and thus can only be made by drilling, punching or the like. Technically, it is very difficult to make the small passage openings in accordance with the required tolerances. This results in frequent disturbances during the working of the transmission unit.